Silicone oil grease containing a phthalocyanine and acetylene black



Sttes SILICONE OIL GREASE CONTAINING A PHTHAL' OCYANINE AND ACETYLENE BLACK Francis F. Sullivan, Oxon Hill, and Hayward R. Baker, Hyattsville, Md, and Curtis R. Singleterry, Arlington, Va., assignors to the United States of America as represented by the Secretary of the Navy Application October 31, 1956 Serial No. 619,643

11 Claims. (Cl. 252-29) (Granted under Title 35, U5. Code (1952), sec. 266) No Drawing.

ture lubricants is critically limited, however, by their rapid deterioration under service conditions at temperatures in the range of 400 to 500 F. This deterioration of silicone oils we have found to result from two separate processes, both of which may be accelerated by the action of atmospheric oxygen. The one process is volatilization of low molecular weight products of oxidation or oxidative fission of the silicone molecule. The other is further polymerization of the silicone oil in the presence of the oxidation products with ensuing gelation of the oil to eventually a semisolid or gel.

We have found that silicone oil greases having a high degree of chemical stability under service conditions at temperatures in the range of about 400 to 580. F., can be obtained by the addition of small amounts of finely divided acetylene black to silicone oil greases which are thickened with a metal phthalocyanine, e.g., copper or chlorinated copper phthalocyanine.

The action of the acetylene black is to strongly retard gelation of silicone oils at temperatures of 400 to 580 F. even when it is used in amounts as small as 0.1% by Weight of the grease composition. Retarding of the gelation is more pronounced'when the acetylene black is used in the grease in conjunction with an oxidation inhibitor which is efiective at a temperature within the indicated range of high temperatures. Suitable oxidation inhibitors of this kind are those of the arylamine type, for example, phenyl-a-naphthylamine, those of the phenothiazine, type, for example, phenothiazine and dilauryl selenide. The oxidation inhibitor may be used insmall amounts, for example, from about 0.5 to 5% by weight depending upon the particular oxidation inhibitor employed. While the finely divided acetylene black may be effectively employed over a wide range of proportions to obtain improvement in chemical stability of the grease at temperatures of 400 to 580 F., it is in general advantageous to employ a metal phthalocyanine as the primary thickening agent so as to obtain optimum grease structure and to add only such amounts as may be required to produce the chemical stability sought in the grease. While amounts of the acetylene black equal to about 7% by weight can be usefully employed in the grease compositions, in general, a practical range of proportions therefor in the greases is from about 1 to 4% by weight of the composition. The acetylene black has been found capable of producing a remarkably high degree of chemical stability in the greases at the indicated high tempera- 2,929,779 Patented Mar. 22, 1960 tures without destroying the good grease strrcture which is to be obtained by use of a metal phthalocyanine pigment, as thickener, or reducing the shear stability and low bleeding behavior of the grease. An added beneficial effect of the presence of the finely divided acetylene black in the grease is in its capacity to remain in a uniform state of dispersion in the grease whereby as a solid it reinforces the inherent plastic structure of the grease.

Preparation of the greases of the present invention can be carried out in the following manner. The finely divided acetylene black and the liquid polysiloxane or silicone oil are mixed together along with an oiliness additive, for example, phcnyl stearic acid and with the oxidation inhibitor, when the same is used. The resulting oil suspension is then heated to degas the acetylene black of adsorbed air, for which it is heated in an oven for about one-half hour at a temperature which is above that at which the grease is to be used in service, for example, at 480 F. for aservice temperature of 450 F. Any liquid polysiloxane may be used as the silicone oil for the greases, for example, polymethylsiloxane, polyethylsiloxane, polyphenylmethylsiloxanes of varying degrees of phenylation (aromaticity), and the liquid halogenated arylsiloxanes as described in US. Patents 2,599,- 984 and 2,642,395. The invention is practiced to the greatest advantage with liquid polyphenylmethylsiloxanes which are lightly phenylated, i.e., those having less than about 15% of phenyl groups in the molecule. Such liquid polysiloxanes possess desirable viscosity-temperature values for the greases. The phthalocyanine pigment powder to be used as thickener for the grease is wet with a minimum of the oil suspension to form a paste, milled on a three roll paint mill to a smooth consistency and the prepared silicone oil mixture then added in small amounts at intervals during the milling. Milling is continued until a smooth paste is obtained. The paste is removed from the mill and heated in an oven for an hour at a temperature which is above that at which the grease is to be used in service, for example, at 480 F. for a service temperature of 450 F. The grease is returned to the mill, worked for several passes, heated in the oven as before and again returned to the mill where it is worked a short time to restore the milled condition of the grease. It is then ready for service use or to be packaged. The heat treatment serves to complete the dispersion of the solids in the grease. Suitable proportions of the phthalocyanine powder for producing the grease structure is from about 18 to 25% by weight of the composition.

Illustrative of improved silicone oil greases which can be prepared in accordance with the present invention is the grease of the following composition.

Percent weight 2 DC510. A slightly phenylated polyphenylmethylsiloxane of 50 centistokes at 77 F.

The new greases are useful as lubricants for ball and roller bearings and have the capacity to retain thei soft and oily texture at temperatures of from about 400 to 580 F. for substantially longer periods than greases of the correspondingcomposition which do not contain the acetylene black. A grease of the composition of the above example will remain soft and oily at 480 F. for.

a period at least three times longer than a greaseof identical composition but lacking the acetylene black.

Since the principle of the inventionherein described may be variously embodied without departing from the spirit or scope thereof, it is intended that the specific embodiment appearing in the above description shall be taken by way of illustration and not in limitation except as may be required by the following claims.

What is claimed is:

1. A semi-fluid composition consisting essentially of a major proportion of liquid polysiloxane of lubricating viscosity, a minor proportion of a metal phthalocyanine suflicient to thicken the liquid polysiloxane to grease consistency'and from about 0.1 to 7% by Weight of finely divided acetylene'black sufiicient to increase the resist ance to gelation of the liquid polysiloxane.

'2. A semi-fluid composition consisting essentially of a major proportion of a liquid polysiloxane of lubricating viscosity, a minor proportion of a copper phthalocyanine sufiicient to thicken the liquid polysiloxane to grease consistency and from about 1 to 7%. by weight of a finely divided acetylene black sutlicient to increase the resistance to gelation of the liquid polysiloxane.

3. A semi-fluid composition consisting essentially of a major proportion of a liquid polysiloxane of lubricating viscosity, a minor proportion of a chlorinated copper phthalocyanine sufiicient to thicken the'li'quid polysiloxane to grease consistency and from about ,1 to 7% by weight of finely divided acetylene black sufficient to increase the resistance to gelation of the liquid polysiloxane.

4. A semi-fluid composition consisting essentially of a major proportion of a liquid polysiloxane of lubricating viscosity, a minor proportion of a copper phthalocyanine sufficient to thicken the liquid polysiloxane to grease consistency and from about 1 to 4% by weight of a finely divided acetylene black suflicient to increase the resistance to gelation of the liquid pol'ysiloxane.

"5. A semi-fluid composition consisting essentially of a major proportion of aliquid polysiloxane of lubricating viscosity, -a minor proportion of a metal phthalocyanine sufficient to thicken the liquid polysiloxane to grease consistency, from about 0.1 to 7% by weight of finely divided acetylene black sufiicient to increase'the resistance to gelation of the liquid polysiloxane and from about 0.5

to by weight of an oxidation inhibitor which is ef- 4 sufiicient'to thicken the liquid polysiloxane to grease consistency, from about 1 to 7% by weight of finely divided acetylene black sufiicient to increase the resistance to gelation of the liquid polysiloxane and from about 0.5 to 3% by weight of phenothiazine to further increase the resistance to gelation of the liquid polysiloxane.

8. A semifiuid composition consisting essentially of a major proportion of a liquid, polyphenylmethylsiloxane oflubricating viscosity and having not more than about phenylation, a minor proportion of a metal phthalocyanine sufficient to thicken the liquid polysiloxane to grease consistency, from about 1 to 7% by weight of finely divided acetylene black suflicient to increase the resistance to gelation of the liquid polysiloxane and from about 0.5 to 5% by weight of an oxidation inhibitor which is effective at a temperature within the range of from about 400 to 580 F. to further increase the resistance to gelation of the liquid polysiloxane.

9. A semi-fluid composition consisting essentially of a major proportion of a liquid, polyphenylmethylsiloxane of lubricating viscosity and having not more than about 15% phenylation, a minor proportion of a copper phthalocyanine-sufiicient to thicken the liquid polysiloxane to grease consistency, from about 1 to 4% by weight of a finely divided acetylene black sufiicient to increase the resistance to gelation of the liquid polysiloxane and from about 0.5 to.5% by weight of an oxidation inhibitor which is effective at a temperature within the range of from about 400 to 580 F. to further increase the re sistance to gelation of the liquid polysiloxane.

10. A semi-fluid composition consisting essential of a major proportion of a liquid, polyphenylmethylsiloxane of lubricating viscosity and havingnot more than about 15% phenylation, a minor proportion of a chlorinated major proportion of a liquid polysiloxane of lubricating viscosity, a minor proportion of a metal phthalocyanine sufficient to thicken the liquid polysiloxane to grease consistency, from about 1 to 7% by weight of a finely divided acetylene black sufficient to increase the resistance to gelation of the liquid polysiloxane and from about 0.5 to 5% by weight of phenyl-a-n'aphthylamineto further ncrease the resistance to gelationof the liquid polysiloxane.

7. A semi-fluid composition consisting essentially of a major proportion of a liquid polysiloxane of lubricating viscosity, a minor proportion of a metal phthalocyanine copper phthalocyanine sufficient to thickenrthe liquid polysiloxane to grease consistency, from about 1 to 4% by weight-of finely divided acetylene black sufficient to increase the resistance to gelation of the liquid polysiloxane and from about 0.5 to 5% by weight of an oxidation inhibitor which is effective at a temperature within the range of from about 400m 580 F. to further increase References Cited in the file of this patent UNITED STATES PATENTS 2,453,153 Morway et al. L5- Nov. 9, 1948 2,486,674 Pedersen Nov. 1, 1949 2,522,460 Morway et a1. Sept. 12, 1950 2,597,018 I Merker May 20, 1952 OTHER REFERENCES Boner: Lubricating Greases, Reinhold Pub. 1954, pp. 690-97, 700-01. 

1. A SEMI-FLUID COMPOSITION CONSISTING ESSENTIALLY OF A MAJOR PROPORTION OF LIQUID POLYSILOXANE OF LUBRICATING VISCOSITY, A MINOR PROPORTION OF A METAL PHTHALOCYANINE SUFFICIENT TO THICKEN THE LIQUID POLYSILOXANE TO GREASE CONSISTENCY AND FROM ABOUT 0.1 TO 7% BY WEIGHT OF FINELY DIVIDED ACETYLENE BLACK SUFFICIENT TO INCREASE THE RESISANCE TO GELATION OF THE LIQUID POLYSILOXANE. 